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Old 08-01-2022, 07:44 PM
pont3 pont3 is offline
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Default Fusible links

Is it acceptable to replace a burnt fusible link with an inline fuse? I can't seem to find the original style wire anywhere. From what I understand, the fusible link wire is a few gauges lower than the circuit it is protecting. So would using an inline fuse of a lower amperage provide the same protection?

The reason I ask is that I replaced the blown fusible link on my '72 with the only thing I could find that is sort of a hybrid, (it is comprised of 14 gage fusible link with a 30 amp spade type fuse incorporated.) However, this fuse gets very hot and although it hasn't blown, the plastic on the fuse is melting.

What's up here? I am going to replace the entire engine harness and if anybody has an original one in good shape I'm interested. Otherwise I have no choice but to consider aftermarket harnesses.

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Old 08-01-2022, 08:59 PM
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If the fuse is getting hot enough to melt the plastic, you are playing with fire. What is that fuse supplying?

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Old 08-01-2022, 09:15 PM
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Napa used to carry Fuseable links in a few amperage. They still may carry generic ones you can solder in line.
Typically in cars. the ones that blow are related to A/C.
Their purpose is to be a " Slow-Blo" fuse. The relay starting the hi-blow on an AC can make it warm. Have also seen a drop top motor cause issues as well if it uses a fuseable link vs a firewall mounted hi heat 30 + amp fuse

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Old 08-01-2022, 11:44 PM
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Quote:
Originally Posted by Radman View Post
If the fuse is getting hot enough to melt the plastic, you are playing with fire. What is that fuse supplying?
Well thanks, that's the reason I'm asking. This particular fusible link shuts down the entire electrical system of the car. What confuses me is that the portions of the "fused" aftermarket "fusible link " has a spade fuse in the middle of 12 gage fusible wire that you splice in to replace the original fusible wire contains a 30 amp spade fuse. It seemed to solve the issue, but the car would still shut down occasionally and the only thing needed for a restart would be to pull the 30 amp fuse and re-insert it. That's when I noticed that the plastic covering on the spade fuse was melting, but the fuse wasn't blowing.

My question, I guess, really is, was there a reason why the factory used fusible links instead of fuses in certain circuitry?

I don't know the answer other than the fusible links were designed to save other electrical circuits from setting the entire vehicle on fire.,

Again, I am acknowledging that I may have a compromised wiring harness, and, I would like to replace it with a GOOD original, if anybody has one.,

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Old 08-01-2022, 11:57 PM
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What about using a 30 Amp Circuit Breaker? Self resetting so you won't get stranded out in the middle of nowhere? All metal or plastic with a protective cover.

https://www.ebay.com/itm/29498309163...kAAOSwKZlieYd1

https://www.ebay.com/itm/13233642402...4AAOSwb9dZxYCP

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Old 08-02-2022, 02:33 AM
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I really like fusible links. When properly installed they absorb temporary overloads that would quickly kill a properly rated fuse. The thing to understand and not violate is the fusible link MUST BE 4 numbers smaller than the wire they are protecting. So a 10 gauge wire needs a fourteen gauge fusible link. Length is just as critical and should be what is specified (although 5-/2" to 6" of fusible link seems to be the norm).

After having the 10 gauge wire from the alternator become one long fusible link when the alternator shorted out internally, I placed a fusible link close to the alternator and it protects the new wiring. Having that big wire glow red and melt away convinced me that protection was needed. Luckily no more shorts and a dozen years later the wiring and link are still in place doing their thing.

Here's a photo of the 10 gauge wire that burned through but not until all the insulation had melted off.
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Last edited by lust4speed; 08-02-2022 at 02:43 AM.
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Old 08-02-2022, 02:52 AM
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One more photo. This one was a destroyed fuse that was a pain to find. One of the blades had come off the fuse. The shunt bar was still good and a test light lit on both sides. The 30 amp shunt in the fuse was good probably because the load wasn't that great, but the blades didn't fit tight in the aftermarket holder allowing a lot of heat to do damage. After several problems with the standard fuse holders arcing out on fuses, I go with a Maxi-Fuse holder using the large fuses (but still rated at the proper amperage).
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Old 08-02-2022, 07:55 AM
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You can certainly replace a fusible link with a fuse if you choose a reliable way to do it. I prefer doing that with my cars. Biggest reason is that it is a royal pain to replace a fusible link vs a fuse.
30A isn't high enough for this. Nor do you want to use a blade type fuse. The purpose of a fuse is to protect the wire and should be placed as close to the power source as reasonably possible.
The max amperage you want to choose is based on the gauge and length of the wire it's protecting.
Is the wiring in your '72 GTO stock? I would guess that the wire you are protecting is a 12 gauge. For a 12Ga wire that is probably only about 5 feet long, a 50A fuse will be fine. A Midi type fuse and holder is a good way to go and is the type I use.

Here's a link to the fuse. I buy all my electrical supplies from waytekwire.com.
https://www.waytekwire.com/item/4638...olt-Down-Fuse/

Here is the fuse holder for those fuses:
https://www.waytekwire.com/item/4639...0-Fuse-Holder/

It's also important that you install ring terminals on the wires in a reliable way. The best way is to use non-insulated terminals and cover them with heat-shrink tubing after crimping them on. You get a much better quality of crimp using non-insulated terminals compared to the insulated ones your local auto parts store carries. However it's easy to convert an insulated terminal into a non-insulated one by applying a bit of heat and then slip the insulator off.

You will want to make sure your crimping tool has a jaw that is for labeled non-insulated terminals. Higher quality tools will have different markings for either insulated or non-insulated. You will need a heat gun and some heat-shrink tubing for this too.
If you are using the cheaper thin-walled heat-shrink tubing, you can double it up for better protection. I buy the heavy-walled adhesive-lined heat shrink tubing that waytekwire carries.

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Old 08-02-2022, 01:56 PM
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I really like those fuses and holders. Have a much more factory look than the ones you get in the stereo section

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Old 08-02-2022, 05:05 PM
TacoTownCharlie TacoTownCharlie is offline
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Iíve been very happy with everything Iíve ordered from Mad Electrical. I know a lot of people on this board have ordered supplies from there as well. He has a good selection of ready to use fusable links and all the tools and instructions needed to install them.

http://www.madelectrical.com

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Old 08-02-2022, 07:50 PM
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Thanks guys for your expertise, these are exactly the types of knowledge I was seeking.

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Old 08-02-2022, 08:28 PM
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You can but fusible link wire from NAPA, or a host of other suppliers:

https://www.google.com/search?q=auto...hrome&ie=UTF-8

It's not hard to come by.

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